The present invention relates to a beam forming device for forming a uniform radiation beam and/or a reception beam. In radiation, the transducer is vibrated in such a way that the pressure of a sound wave produced from each point of the vibrating surface of the transducer is determined based on a weight function, thereby forming a radiation beam. In reception, electric signals are derived based on the sound energy received in a manner that the amplitude level of an electric signal produced based on the sound energy received by each point of the vibrating surface of the transducer is determined based on a weight function, and the derived signals are combined with one another to form a reception beam.